Compositions of epoxy resins cured with organotin compounds

ABSTRACT

Epoxy resins cured with organotin compounds provide electrical insulation which is characterized by good dissipation factor, high-heat distortion temperature and good corona resistance.

United States Patent Mark Markovitz;

Leo S. Kohn, both of Schenectady, N.Y. 757,168

Sept. 3, 1968 Nov. 23, 197 1 General Electric Company Inventors App].No. Filed Patented Assignee us. c1 260/2 EC, 117/161 28, 161/184 R,260/18 EP, 260/47 EC, 260/59 R, 260/4297 R, 260/830 R 1111.01 cos; 30/10[50] Field of Search 260/2 EP, 2 CN, 18 EP, 47 EP, 59, 830 TN, 429.7;252/182 [56] References Cited UNITED STATES PATENTS 2,803,609 8/l957Schlenker 260/47 3,l47,285 9/1964 Mack 260/2 EP 3,244,670 4/1966Puchalaetal. .1: 260/47 EPC Primary Examiner-William H. Short AssistantExaminerT. Pertilla Anomeyswilliam C. Crutcher, Joseph B. Forman, FrankL.

Neuhauser, Oscar B. Waddell and Harold J. Halt ABSTRACT: Epoxy resinscured with organotin compounds provide electrical insulation which ischaracterized by good dissipation factor, high-heat distortiontemperature and good corona resistance.

COMPOSITIONS OF EPOXY RESINS CURED WITH ORGANOTIN COMPOUNDS Thisinvention relates to epoxy resin compositions and to curing agentstherefor. More particularly, it relates to new and useful epoxy resincompositions which are characterized by improved high voltage,electrical insulating qualities.

With the development of electrodynamic machinery which operates athigher and higher voltages, there has developed a corresponding need forelectrical insulating materials which will keep pace with more rigorousrequirements such as ability to operate at higher operating temperaturesand at corona producing voltages, all with electrical losses which arekept at a minimum. Generally speaking, it is relatively easy to findelectrical insulating materials such as resinous materials and the likewhich will have one or several of the desirable electrical insulatingqualities which are sought for high-voltage operation of electricalmachinery. However, it is seldom that one finds within a singleelectrical insulating material a community of properties which suits italone for such rigorous operation. For example, silicone resins ingeneral are characterized by very good corona resistance. However, atelevated temperatures over a period of time, such silicones often formrubbery materials which have a relatively low heat distortiontemperature which results in low tensile, flexural and compressivestrengths and ultimate failure under the mechanical stresses to whichthey are subjected in modern rotating equipment.

From the above it will be evident that there is a definite need forelectrical insulation which will combine in one material adequateresistance to the various electrical and mechanical stresses which areexperienced in high-voltage electrodynamic machines and it is a primaryobject of this invention to provide such materials.

It has been unexpectedly found that epoxy resins cured with certainorganotin compositions are very well suited for electrical insulatingpurposes either as such or in tapes and the like which are not onlycorona-resistant under high-voltage stress but which also have a veryhigh heat-distortion temperature with its accompanying good physicalqualities such as tensile strength, flexural strength and the like andwhich at the same time have a very low dissipation or loss factor atelevated temperatures and voltages and resistance to corona damage.

Those features of the invention which are believed to be novel are setforth with particularity in the claims appended hereto. The inventionwill, however, be better understood and further advantages and objectsthereof appreciated from a consideration of the following description.

Generally speaking, the organotin compounds of the present invention areused with epoxy resins in amounts of from about to 120 parts by weight,and preferably 80 parts by weight per 100 parts of epoxy resin.Additional acidic or anhydride material can also be used.

Any of a number of organotin, specifically organostannoic, materialssuch as the oxide or materials which produce the oxide can be used inconnection with the present invention. Generally speaking, dialkyltinand diaryltin oxides and combinations are preferred, includingtypically, dimethyltin oxide, butyl propyltin oxide, dihexyltin oxide,diphenyltin oxide, di(4-methylphenyl)tin oxide, phenylbutyltin oxide,and the like. Other organotin materials such as esters typified by theacetate, propionate and laurate, among others, and halides such as thechloride, bromide and iodide, which provide for ready entry of the tininto the organic composition can be used.

The tin-containing moiety is reacted with organic acidic or anhydridematerial to form the epoxy resin hardener or crosslinking material.Among such acidic materials which are useful are sebacic, succinic,glutaric, adipic, pimelic, suberic, azelaic, dimerized unsaturated fattyacids such as Emery Chemicals Empol 1010 Dimer Acid, isophthalic andterephthalic acids. Organo-functional carboxylic acids such asamino-functional materials as e-amino caproic acid, p-amino benzoicacid, m-amino benzoic acid, glutamic acid, and methionine may be used.Hydroxy-functional carboxylic acids can also be used, such asp-hydroxybenzoic acid, m-hydroxybenzoic acid, 7-hydroxyheptanoic acid,and 4-hydroxy-4'- carboxybiphenyl acid. Among the anhydrides which canbe used are the maleic anhydride adduct of methylcyclopentadiene knownas Nadic Methyl Anhydride made by Allied Chemical Company,hexahydrophthalic anhydride, phthalic anhydride, tetrahydrophthalicanhydride, methylsuccinic anhydride. dodecenylsuccinic anhydride,Alkendic anhydride, polymeric anhydrides such as polyazelaicpolyanhydride, chlorendic anhydride, tetrabromophthalic anhydride, andthe like. From a consideration of the above, other suitable materialswill occur to those skilled in the art.

Generally speaking, the organotin material is reacted with the acidicmaterial in equivalent proportions although excesses up to 50 percent ofeither material can be used. The following examples illustrate thepreparation of the present organotin cross-linking or curing materials.

EXAMPLE A A mixture of 303 g. (1.5 moles) sebacic acid and 373.5 g. 1.5moles) dibutyltin oxide in 1,050 g. of benzene was stirred and refluxedin a flask attached to a Dean-Stark receiver. After 4.5 hours at 7283C., 26 g. (theoretical 27 g.) of water collected in the receiver and thesolids initially present had nearly all dissolved. The reaction mixturewas filtered to remove the remaining 0.5 g. of insoluble material andthe filtrate was distilled at atmospheric pressure and in vacuum toremove the solvent to leave a clear, yellow-orange oil which solidifiedat room temperature and became a free-flowing liquid at C. The tincontent of the product was from 26.7 to 27.6 percent.

EXAMPLE B This example illustrates the preparation of a butyltin oxideand p-aminobenzoic acid reaction product. A mixture of 249 g. (1.0 mole)dibutyltin oxide and 274 g. (2.0 moles) paminobenzoic acid in 1,050 g.of benzene was stirred and heated in a flask attached to a Dean Starkreceived. After 2 hours at 70-80 C., 17.5 g. (18 g. theoretical) ofwater was collected in the received and the reaction mixture wasfiltered to remove a small remaining quantity of solids. The filtratewas distilled at room atmospheric pressure and then under vacuum toremove benzene, leaving a yellow oil which solidified to a glassymaterial at room temperature and then slowly crystallized to form verylarge white crystals. Subjection to infrared analysis indicated nounreacted dibutyltin oxide or p-aminobenzoic acid. The reaction productwas freeflowing liquid at 160 C. and the tin content was 22.9 to 23.7percent.

EXAMPLE C This example illustrates the preparation of an epoxy resincross-linking material from the reaction of dibutyltin oxide andp-hydroxybenzoic acid. A mixture of 249 g. (1.0 mole) dibutyltin oxideand 276 g. 2.0 moles) p-hydroxybenzoic acid in 600 g. of benzene wasstirred and heated in a flask with a Dean-Stark receiver. After 3.5hours at 71 to 81 C., 17.5 g. (theoretical 18 g.) of water wascollected. The reaction mixture was filtered to remove 1 g. ofundissolved material and the clear, pale, amber filtrate was distilledat atmospheric pressure and under vacuum to remove solvent. Theremaining clear yellow oil residue solidified to a glassy material atroom temperature and had a tin content of 22.8 to 23.6 percent based onthe tin content of the dibutyltin oxide. It turned to a liquid at atemperature of approximately 150 C.

EXAMPLE D This example illustrates the preparation of a dibutyltin oxideNadic Methyl Anhydride (NMA) cross-linking agent. A mixture of 500 g.(2.81 moles) Nadic Methyl Anhydride and g. (0.50 mole) dibutyltin oxidewas stirred and heated, the

dibutyltin oxide dissolving at a temperature of about 128 C. Thereaction mixture was stirred an additional 2 hours at 128l 43 C., givinga clear, pale, amber oil which solidified at room temperature to a soft,waxy solid and which liquified at approximately 100 C. The tin contentof the product based on the tin content of the dibutyltin oxide used was9.3 to 9.6 percent.

EXAMPLE E This example illustrates the preparation of a cross-linkingagent from Nadic Methyl Anhydride and dibutyltin oxide. A mixture of 375g. (2.1 1 moles) Nadic Methyl Anhydride and 250 g. (LOO-mole) dibutyltinoxide was stirred and heated for about l hour at 75-160 C. and then for1.25 hours at l61l 73 C. The clear, amber oil produced solidified atroom temperature to a waxy solid which became pourable at about 125 C.The tin content of the product based on the tin content of thedibutyltin oxide was 18.6 to 19.2 percent.

Any of the usual epoxy or ethoxyline resins having 1, 2 epoxy groups areuseful in connection with the present invention. Included are the usualbisphenol-A diglycidyl ether epoxy resins as well as those derived frompolyolefin or glycerides or oils. Among other useful epoxy resins arethe socalled epoxy novolac resins and cycloaliphatic epoxy resins. Suchresins are well known in the art and some are set forth, for example, inUS. Pat. Nos. 2,324,483; 2,444,333; 2,494,295; 2,500,600; and 2,511,913. Mixtures of epoxy resins can also be used. Among the specificepoxy resins used in exemplary manner in the following examples are Epon828 of the Shell Chemical Company which is a liquid diglycidyl ether ofbisphenol-A having an epoxide equivalent weight of from 185 to 192. Epon1001 is normally solid bisphenol-A diglycidyl ether reaction productmade by Shell and having a melting point of from about 65 to 75 C. andan epoxide equivalent weight of450-550.

Epoxy novolac resins are typified by Dow DEN 438 which has an epoxidefunctionality of 3.6 and an epoxide equivalent weight of 175-182. Thismaterial may be expressed by the formula Very useful in connection withthe present invention are cycloaliphatic epoxy resins having 1,2 epoxygroups which are typified by ERLA 4221 having an epoxide equivalentweight of 126 to 140, manufactured by Union Carbide Plastics Company andhaving the following formulation Still another useful epoxy resin isCY-175 (Ciba Products Company) having an epoxide equivalent weight ofabout 160 hours at C. in order to attain uniform treating conditions.However, it will be realized that for many of the examples, lower curetemperatures and shorter cure times are entirely adequate.

EXAMPLE 1 Shown in table 1 below are various results obtained when ERLA4221 epoxy resin was cured with a mixture of the dibutyltin oxidesebacic acid reaction product of example A along with the Nadic MethylAnhydride (NMA) to speed the cure, all materials being in parts byweight as shown. Shown in the table is the dissipation factor cured asabove at various temperatures and the heat distortion of the material at264 p.s.i. using samples 5X /z inches according to ASTM D648-56. The tenmils deflection was taken as the heat distortion temperature. Also shownin the table are the tensile strengths and elongation for the abovematerials.

TABLE I Parts by Parts by Parts by weight weight weight E RLA 4221 30 3030 BuzSnO-sebaeic (Example A) 30 30 30 NMA 10 20 30 Sn content, percent11.4-11. 8 10. 0-10. 4 8. 9-0. 2

Dissipation factor (tan 6) Temperature, (3.:

Heat distoi'tion ag2fi4 p.s.i., temp,

Mils deflection:

01 103 83 10 (HDI) U!) 112 81) Tensile strength at 25 C., p.s.i. 4. 5004, 300 Elongation at break, percent 1. l 1.8

It will be noted from table 11 above that the corona resistance of thepresent materials is far and away greater than that of other typicalmaterials with the exception of silicone rubber. However, it will beappreciated, as pointed out above, that while silicone rubber has goodchemical resistance, its heat distortion and physical strength may havemuch to be desired where such characteristics are required.

EXAMPLE 2 TABLE v Shown in table III below are the dissipation factorand heat g i j l f distortion characteristics of dibutyltinoxide-sebacic acid and Number 1 2 3 4 Nadic Methyl Anhydrlde curedcycloaliphatic epoxy resin 5 Epon 828 m 9 materials, CY-l 75. DEN 438 5553. s 615 BmSnO-p-aminobenzoic acid (Ex. B 40.1 45 41. 4 37. 5 Sncontent, percent 9. 2-9.5 10.3-10. 7 9.5-0. 8 8. 6-8. TABLE 111 MDissipation factor tan (60 cycles, 10 Parts by Parts by Parts by 0v.p.m.) weight weight weight Temperature, 0.: C Y 175 30 30 30 25 0.0037 0.0041 Bu SnO-sebacic (Ex. A). 30 30 30 100 (I) 0. 0022 O. (102!) A10 20 30 130 0. 0016 0. 0021 Sn content, percent 11.4-11. 8 10. 0-104 8.n4], 3 155... 0. 0042 0. 001 l. 7 H5. (I) 0. 02s l 0 004] Dissipationfactor (Inn at (00 cycles. 10 v.p.ni.) Hunt distortion :ll .(H v s l 7W-We hunpnnnnrn. i, lt-n1pcl'aturc, C.:

25 000075 0) n, 0011 Alils deflection: 100. 0.0023 1 0,021 1 in H4 n1315:1 130 0,01 1 0.03 133 152 ms nu I55 0. 054 0. 05s) 10 (HDT) 140 152417; 100

IIeat distortion at 264 p.s.i., I Not determined. temperaturc, C. V

EXAMPLE 6 V 7 e e The dibutyltin-p-aminobenzoic acid reaction product ofexample B was combined with epoxy resins, Epon 828 and DEN EXAMPLE 3 4381n the proportions shown in table Vl below, the resulting Very hard,clear, amber castings which were extremely materials being very hard andhaving the other characteristics tough and self-extinguishing wereprepared by curing an shown in table VI below. epoxy resin, specificallyEpon 828, with the dibutyltin oxidesebacic acid product of example Aalong with catalytic amounts of 2-ethyl-4-methylimidazole (EMI). Thedissipation TABLE VI factor and heat distortion of various compositionsof such Parts by Parts by materials are shown in table lV below. mightEpon 828 59. a DEN 438 58. t3 Bu sno-paminobenzoic acid (Ex. 40.1 41.4 0Sn content, percent 0. 2-9. 5 0, 5-0. 8 TABLE IV Tensile strength at 250., psi. 4, 000 3, 700 Percent elongation at break 2. 4 1. 4 Parts byParts by Parts by P s y Flexural strength at 25 0., p.s.i 0, 600 14, 000

weight weight weight weight M Epon 828 50 50 60 60 Bu SnO-scbacic Ex.

A) 5O 50 40 40 Shown in table VII below 15 a comparison of the epoxy EMI 1.5 2.5 1.5 2.5 resins of example 6 above with other typical epoxyresins and 133-136 0-1: IDA-10's other resinous materials insofar asregards corona resistance Dissipation factor which was measured in thesame manner as for table II above.

Tan 6 cycles, 25 TABLE Vll Sam le A .f 'l t Heat distortion at 264p.s.i. p vg ure E on 1004 asolid bis h n l-A di l cid l therr action 18hour 0 6 71 P P e 0 sy y e e 5 p 1 C 65 5 product having amelting pointof from about to "C V and an epoxide equivalent weight of 875-1025Polyester polyacid.

5 5 Epon 100i Naminoethylpiperazine 17 hours ERLA 422l n ovolac typephenolic resin 33 hours EXAMPLE 4 Polyethylene terephthalate Zl hoursAromatic polyimide 41 hours Useful resins were also obtained by using asa curing agent Ewaslusgg Pans)iguzsnqpamimbenzoic acid 64 hours thereaction product of 1.5 moles of dibutyltin oxide and 1 (Example B)(40.1 parts). mole of sebacic acid reacted similarly to example A. Theor- DEN (53-6 pmsFfluzsno-Framinflbenzvic acid 89! hours 60 (Example B)(41.4 parts). ganotm material contained 31.2 to 32.2 percent tin. Acasting silicone rubber M 0 re than prepared from 30 parts ERLA 422lepoxy resin, 30 parts of 5'000 hours, the dibutyltin sebacic acidmaterial and 30 parts of Nadic Methyl A'nhydride had a dissipationfactor at 60 cycles of EXAMPLE7 O 0 O 00047 at 100 and 65 The dibutyltinoxide-p-hydroxybenzoic acid reaction at product of example C was meltedby heating to C. and EXAMPLE 5 mixed in various proportions with epoxyresins as shown in table VIII below which were also heated to 100-l50 C.The The dibutyltin oxide-p-aminobenzoic acid reaction product resinswhen cured as above produced tough, hard, clear, yelof example B wasmelted at C. and then mixed with Epon 70 low solids. In the case of theNadic Methyl Anhydride, it was 828 or DEN 438 in the proportionsindicated in table V below. found that dissolving 20 parts of thismaterial and 80 parts of The clear resin solutions remained clear whencooled to room the material of example C lowered the melting point ofthe temperature and cured as above to hard, clear, tough, amber combinedhardener so that it could be mixed with epoxy resins solids havingdissipation factors and heat distortion qualities at 75l00 C. Shown intable VIII below is the dissipation facas shown in table V below. 75 torfor various combinations of the above materials.

m TABLE Vlll Shown in table Xlbelow are the heat distortion charac by byby by teristics of various combinations of epoxy resins and the dibu-W001i K WWW Wight tyltin oxide Nadic Methyl Anhydride material ofexample D.

There are provide, then, by the present invention epoxy mm 4314 A resinhardeners and epoxy resins cured therewith, the latter of fjfbfg zfminwhich are tough, hard, transparent, homogeneous materials (lcxiim ln :0which are not degraded by elevated temperatures and which "final!211mare resistant to corona damage. Large, void-free castings are(0x11110000) NMA v0 10 readily prepared from the materials since novolatiles are snl imiln, {wi t-nil i' iiiiiijii ll. 2'0 1.0770 1.0 informed durins reaction- The materials. because of qrfishbh'tiw{rm-t0;ml-3 cmm Y the presence of organotin compounds, have fungicidal properties.The epoxy resin compositions described herein can be M used asadhesives, coatings, encapsulating and potting com- 0'0032 M039 mm" 1 5pounds, as insulators in high voltage applications, as binders 0. 00700. 0032 0.0037 0.0030 for micaceous and other types of tape, as bindersand prepregs 818g "(38% 8: 9,83,, and other laminated structures and infilament winding appli- 0. 12 0.15 0. 045 0.040 cations. The materialscan be readily filled with well known fil- 175 0'08.) ICIS as desired,and can be formulated to form molding and EXAMPLE 8 20 fluid bed powers.

What we claim as new and desire to secure by Letters Shown in table IXbelow are the dissipation factors of comipa m of he United State ibinations of dibutyltin oxide and Nadic Methyl Anhydride 1. An epoxyresin having I, 2 epoxy groups and from about reaction roduct of exampleD with various epoxy resins as in- 20 to 120 parts by weight per I00parts of epoxy resin of a dicated. DB8 is an accelerator and is aproduct of the Argus hardener which is the reaction product in a leastequivalent Chemical Company.

amounts of a material selected from the group consisting of TABLE IXDlsslpatlon factor v, temperature E RLA 4221 40 50 00 CY-l75 N438 40 00NMA-limSiiO (Ex, 00 40 7O 00 00 50 40 B8 l l 1 1 1 1 1 1 Sn coiituiit,i(irci-.iit.. 5.55.7 4.0 4.8 30741.8 0.4-0.7 5. 5 5.7 5.55.7 4.6-4.83.7-3.8

Dissipatlon factor tan 5 cycles, 10 v,p,m,)

EXAMPLE 9 organotin oxide, organotin ester and organotin halide in whichthe organo group is selected from the group consisting of dialkyl,diary] and aralltyl, and organic acidic material selected from the groupconsisting of dicarboxylic acids, aminofunc and mixtures thereof.

2. An epoxy resin as in claim 1 in which the hardener is tionalcarboxylic acids, carboxylic acid anhydrides thereof TABLE X present inan amount of about parts by weight per parts Dissipation factor v.tumperatum 50 1 f epoxy resin ,,,X,,; 55 E 2 3. An epoxy resin as inclaim 1 in which the material is dibu- :Z-etliyl-4-iii0tliylimidaz0l0. Bityl tln oxide. Sii i-oiitunt, pnrvmit... 0. 2-0.6 7. ti 7. (l

Dissipation MW 4 An epoxy resin as in claim 1 in which thematerial isdibu (00 cycles, 10 v. .m. 55 tyltin diacetate. 'IHIIIINJ'ILLHI'Q, (2.;I mp 5. An epoxy resin as in claim I in which the material is dibu- 20.0.00:: 0. 70 0.0030 0.0020 W d'chkmde- 100. 0.0030 0.0033

'lAllLE xi icitnx 422i. 40 00 00 n u u f (lY--l7fi. :10 40 00 l)liN4lili 40 00 00 NMA lluzSliO (Ex. 1))... 00 00 40 70 00 40 00 00 40 mii 1 l l l l l i i 811 (.Ofltmlt. 115 6.7 4.04.0 0.7-3.0 0.40.7 0.1M. 73.7 3.0 5. 0 0.7 4. 04.8 3.7 3.1-1

Temperature, (1.

Mils dellectloiiz 121 140 75 157 01 115 100 5. 142 157 92 142 164 103131 112 10 (HDT) 161 143 103 168 114 137 110

2. An epoxy resin as in Claim 1 in which the hardener is present in anamount of about 80 parts by weight per 100 parts of epoxy resin.
 3. Anepoxy resin as in claim 1 in which the material is dibutyl tin oxide. 4.An epoxy resin as in claim 1 in which the material is dibutyltindiacetate.
 5. An epoxy resin as in claim 1 in which the material isdibutyltin dichloride.